Health experts in this country want pregnant women to stay away from alcohol, despite Danish research suggesting low to moderate drinking during pregnancy may be OK.

The Danish researchers produced a series of five papers looking at the effects of low, moderate, high and binge drinking on five-year-olds.

Published this week in the journal BJOG: An International Journal of Obstetrics and Gynaecology, the study looked at the effects of alcohol on IQ, attention span, executive functions such as planning, organisation, and self-control in five-year-olds.

Overall, the researchers found that low to moderate weekly drinking in early pregnancy had no significant effect on neurodevelopment of children aged five years, nor did occasional binge drinking.

However, high levels of alcohol intake - nine or more drinks per week - was associated with lower attention span among five-year-olds.

The researchers also concluded that safe levels of alcohol use during pregnancy had not been established.

"Consequently, women should be advised that it is safest to abstain from using alcohol when pregnant," they said.

Despite that, some overseas news organisations have reported the study as proof that drinking in moderation during pregnancy is safe.

Christine Rogan from Alcohol Healthwatch said such studies "do not provide a reason for pregnant mums to pop the champagne".

"There is no such thing as a safe amount of alcohol for a fully mature adult only degrees of risk," she said.

"The risk to adolescent brain development is recognised and delayed onset of drinking advised, so why expose children and unborn babies to it?

"The advice to avoid alcohol during pregnancy, when planning pregnancy and when breastfeeding remains the best, most valid and wise option for women to follow."

Associate Professor Kathryn Kitson, from Massey University's Institute of Food, Nutrition and Human Health, wanted reports on the study to emphasise that as few as nine drinks a week showed association with an increased risk of attention problems in children.

That endorsed no drinking in pregnancy if a cautious safety recommendation was applied, Kitson said.

An example of such a recommendation was of 1000-fold or less levels of exposure to a toxin below the limits that indicated damage. On that basis a "safe" limit should be around 0.009 drinks a week, "essentially no alcohol at all".

Alcohol altered fetal development by interfering with intricate mechanisms that regulated switching genes on and off at critical development stages.

"There is no known safe limit for drinking in pregnancy, and the results of this study actually endorse that message, if correctly reported."

Professor Jennie Connor, head of the Preventive and Social Medicine department at the Dunedin School of Medicine, said there was a risk the Danish studies could lead women to believe it was reasonable to drink during pregnancy as long as it was not too much.

"This research does not establish a safe level of drinking, as the authors themselves point out," she said.

The detrimental effects of exposure to heavy drinking in utero on cognitive function and behaviour in children was well documented.

It was difficult to study drinking in pregnancy because of difficulties in getting good measures of intake in situations where such behaviour was stigmatised, Connor said.

She wanted to see strategies to promote non-drinking households during pregnancy, and a focus on the value of abstaining from alcohol, smoking and other drugs in order to give babies the best possible start in life.